To me, color descriptions convey more than just age. I think of richness, whether I might expect more red fruits than black fruits, etc. It gives me a better overall sense of what to expect. For example, if I read a TN that says a wine is "a light ruby" I might think of a young Burgundy and start thinking of raspberries. It's just part of the sensation, imo.
I typically use the color descriptions from the Windows on the World Wine book.